Gas discharge lamp



y 3, 1950 M. PENNYBACKER 2,599,071

GAS DISCHARGE LAMP Original Filed May 29, 1945 Miles Penzgbaaiver IN V EN TOR.

"ing 180 degrees.

Patented May 23, 1950 GFASEDISCHARGEFLANEP Miles Pennyhacker fiedding Conn.

flfigmall application May 29, 1 9455, "Serial! N0.

$963360, Y nniw EABatent N0. "2;44ll;832, dated" May "This invention relates to electrical lamps .of .the gaseous discharge type, ..employing a .positive holumngas discharge. Y The .lpresent application isa division of mysepending application, Serial #596,360, filed May 729, 1945, entitled fGas .dischargelamnflnow matured into Patent v.#'2 ,'4 l($6.32,,,fissued on .May 4, .1948.

IDsit'ille columngasdischargelampsare usually constructed inthejform .ojiarelat'rvely'long and narrow cylinder of glass, guartzor othensditaQble transparent or translucent material, ,provided with suitable electrodes atboth endgthereof. ,In

,one widely used form, theinternal surface of the :for general illuminatingpuiposes. When'hereinafter using the term transparent;.I do so inthe broad sense, including-the lesser degrees of transparency commonlytermed translucency;

For most purposesit is desired that the ilight "from a lamp be emittedover an arcof not exceed- Accordingly, when a -cy1indricalm-shape lamp is employed, it is usually found necessary, or at least highlydesiraiole, to employ a refiectcr which will-render available "ii-portion of the light otherwise wasted by reason -of:the fact that it is emitted in an untiesirabledirection. I

-One object of this invention is to provide a 0 novel form of elongated cylindrical lamp from which the externally available light is emitted substantially wholly "along one jlongitudinal half of thecylincler, thus causing the luminous output 'of the lamp t0 be completely available without the need of employing an "external -reflector.

Another purpose of this invention is to provide -a= t.ibular lamp with an internal reflector, inthe form of an element not closely connected, either mechanically or chemically, with "the internal wall of the tube, in distinction from reflecting elements which have hitherto been formed as metallic deposits, or the "like, uponsuch-internal Wall, and which reflector may alsoac't as a support-fora fiuoresoentooating.

A still "further purpose of this invention zls'to provide a tubular lamp in which the reflector can be manufactured independently :of -the-.-tuhe and only inserted therein when the tube=isrready 'ito be:'sealed. This discrete construction is well adapted to -economical large scale production, in ;contrast to certain hitherto ,-;employecl methods of constructing an internal reflector, -.-in esitu, 'with-inf-lihe tube itself.

- =Qther purposes and-advantages of .this :dmrenimanurlaeture and. operation 1 tionwill be apparentto .t'hose skilledjin the art from the followingdescription of several embodiments'thereo'f.

Reference is now made "tothe drawings hereunto attacheol, where:

Fig. "1. is aperspective viewofatubezenrbotlying one-form oithis invention,

Fig. 2A is a ,cross-sectionalview of the tube of 'Figgl, and

"Fig. 2B is across-sectional view cf a' tube em- -"-bodying another "form oi" this *invention.

Referring now tor'igs. l and 2A, there is shown an elongated tube I of suitable gas-con- "fining material, sueh-as glass. This material is chosen to he transparent to radiations having such wave lengths as are to be utilized ex'tenna lly. For-example,the tube ma-y'he constructed-of ultra violet transmitting glass pr oiquar tzfli f theradiap 'tions lie the-ultra violet portion of theispectrum. Suitable electrodes 'o f the cold cathede type, 2, are shown :at each end of the "tube, but hoteathodes may optionally be-used. rExt-ending longitudinally of the tube, :but aprefienab'ly Eater'- -minating short of each velectrode is -:a :refiectmg :s'TrripS. Asshcwn niEig.ii2;A,itdszpreieisredrthat -this Est-rip :extend for approximately $89 degmees :aroundthe'rinternaliperipherymfithe ituehe. How- :ever, strips extending over a greater or :lesser :angle maybe employed "without departure ifrcm this invention. Strhe iormed 20i 'suttaihle reflective material which will withstand thertemperature and treatment incidental to the the tube. :Such mmaterial :sheulrl be {capable xef ready deegasificationand should -not-evol gezgases duringropeeation of the tube. EForvreasons hereinaf'tento be ex --.plaie;edvin :detai-l, TI preter to ,thisastrip of hempaeati-rely thin metal or alloy, possessing :some degree :of elasticity. ssuitahle :matenials include iron, nickel-plated :irom, magnesium and aluminum, -,-but this invention is not :confined :to the employmentrof lthesepar-ticularjmetals. ZIIhe strip may he sprungin-to ,ajsemiacylindrical ,forin,

.as it ,being inserted into .-.the tuba-or prior'to ysuchl-iuseution therein. ThG'sBIaSKiCitY-Qf1311015131111) is possihleto monntnriastsn .thestripin place by any othermeans.

jIn EigMZB there isshown a .variantionn .3.

e which the .strip Just described may assume. In

this particular form, the apex of the V and extremities of the two arms of the V constitute three lines of contact extending longitudinally along the tube wall. The tendency of the V to expand laterally may be used to hold the strip in place.

Evidently the surface of the reflecting strip should be chosen of a nature to act as an eflicient reflector for the particular wave lengths which are to be emitted from the tube.

For confinin the positive column discharge to the proper path thereof, it has been found desirable but not essential that the surface of a conducting reflecting strip which faces this path within the tube be covered with a layer of insulating material I. If the material constituting the surface of the reflector strip be metallic in nature, it may be desirable to place over it an outside layer of some material which is relatively transparent or reflecting, but which is also non-conducting. Many white materials such as aluminum oxide, magnesium oxide, or

other metallic oxides, and the like, function both as a suitable translucent and reflecting surface and as a suitable insulator. A material such as aluminum oxide also functions well in cases where reflection of ultra violet radiations, as well as visible, is desired. Such insulating materials act simultaneously as reflectors and as insulators to prevent or at least to minimize passage of any substantial amount of current through the reflector strip, when this strip is formed of a conductive material such as a metal.

In the case of gas discharge tubes of the fluorescent type, the visible light proceeds from a material which is usually non-conducting and only somewhat transparent. Such phosphors may be used to cover the surface of the reflecting strip, in which case the material functions not only as a light transmitter and emitter, but also to a certain extent as a light reflector.

In certain embodiments of this invention, the longitudinal wall of the tube opposite such a strip coated with a reflective phosphor is relatively transparent, and inversely related to the are covered by the relatively opaque reflecting strip. As the reflecting strip is made to extend more than 180 degrees, the light will be emitted throughout an arc correspondingly less than 180 degrees. This arrangement will in many cases eliminate the need for external reflectors. By my use of a separate reflector strip bearing the phosphor, such type of lamp may be manufactured very simply, whereas it has been found very difiicult to coat the internal wall of a tube over only a portion of the periphery thereof.

In the particular form of construction just described, employing a fluorescent coating, it is evident that the luminous efliciency of the lamp will be increased, at least as far as light emission in a desired direction is concerned, in comparison with a fluorescent lamp having the interior surface completely coated with the phosphor. Furthermore, it is possible with this invention, to apply the phosphor in a relatively thick coating to the reflector strip without thereby bringing about loss of efficiency, for reasons which have previously been mentioned. The possibility, thus secured, of using a relatively thick coating of phosphor leads to ease in manufacture, since such coating may be applied with a considerable factor of safety above the minimum thickness required to cover the strip.

1 Measurements made upon a fluorescent type tube employing a reflecting strip covering approximately 180 degrees, and covered with a phosphor, showed a luminous output, over approximately 180 degrees, of 33 units in comparison with 23 units from a similar tube, drawing the same amount of electrical energy, but employing a phosphor distributed over the entire inner surface of the tube, according to the hitherto prevailing practice in the art.

In many cases, and particularly in the case of the form of strip of Fig. 2B, it is preferred that an insulating coating cover the rear of the reflector strip also in order to prevent possible electrical discharge to or from this side of the strip.

It will be evident that for ease in replacement, it will be desirable that the reflector strip be placed within the tube at a predetermined angular relationship to the contact-making pins usually provided in pairs, at both ends of the tube. This will ensure that, when a fixture or other device mounting the two sockets in which the tube is to be placed has once been put in position, the reflecting strip will be found in the desired position relative to the direction in which the useful output is to be radiated. In the case of direct lighting, this direction usually will be downward and no external reflector will be needed. In the case of indirect lighting, the direction will usually be upward or sideward, but no shield between the light source and the eye will be needed because of the opaque strip in the lamp. In either case, the strip serves as a reflecting surface or secondary light source which cannot be reached by dust and dirt.

Among the novel advantages of that form of this invention which embodies a separable strip is the fact that the actual application of the insulating or fluorescent material does not have to take place within the relatively narrow confines of the glass tube. The strip is preferably coated before insertion in the tube, thus making possible coating methods not so readily applicable to coating the inside of glass tubes. These methods permit the use of fluorescent powder or pigments which do not have to be subjected to the prolonged grinding or ballmilling now customary in making suspensions for coating the inner surfaces of fluorescent lamps.

The less the grinding of the fluorescent particles, the more eflicient they are. Likewise, less care will be needed in applying this coating than is needed in applying it to an ordinary fluorescent lamp, since excess thickness upon any portion of the strip will not give rise to uneven illumination of the bulb. I have found that coatings made from the usual fluorescent silicates may be as much as several thousandths of an inch in thickness.

It is often advantageous to combine in one element a reflector and a starting strip. This embodiment of my invention is described in my copending application, Serial #569,488, filed December 23, 1944, now matured into Patent #2,451,043, issued on October 12, 1948.

While there have been described certain nonlimiting forms of this invention, other forms will be apparent to those skilled in the art, and the scope of this invention is limited only by the hereunto appended claims.

I claim:

1. A positive column gas discharge lamp with self-contained reflector, including an elongated tube formed of light transmitting material, an ionizable' gas confined within said tube, at least two electrodes situated near the respective ends of said tube, a single metallic reflector strip extending the major portion of the distance between said electrodes and having one of the surfaces thereof lying closely adjacent to a portion of the interior wall of said tube, and means for preventing current flow through said reflector strip, said last means comprising a porous coating overlying the major portion of the interior surface of said strip, said coating being formed of discrete particles of insulating and at least partly light transmitting material, said coating thereby ofiering a material electrical resistance to the establishment of a current discharge therethrough, whereby current flow via said strip is minimized, and whereby reflection from said strip occurs through said coating.

2. A positive column gas discharge lamp with self-contained reflector functioning over not substantially more than 180, including an elongated tube formed of light transmitting material, an ionizable gas confined within said tube, at least two electrodes situated near the respective ends of said tube, a single metallic reflector strip extending the major portion of the distance between said electrodes and formed as a trough, of which the interior surface is exposed to the positive column discharge, and means for preventing current flow through said reflector strip, said last means comprising a porous coating overlying the major portion of the interior surface of said strip, said coating being formed of discrete particles of insulating and at least partly light transmitting material, said coating thereby offering a material electrical resistance to the establishment of a current discharge therethrough, whereby current flow via said strip is minimized, and whereby reflection from said strip occurs through said coating, said trough having a V-shaped transverse cross-section, making contact with the walls of said tube along three substantially parallel lines, thereby dividing said tube longitudinally into three elongated sections, and in which said electrodes are located substantially in the axis of said tube, whereby the positive column discharge is confined substantially to the interior of said V-shaped trough.

3. In an elongated positive column discharge lamp, including a gas filled transparent envelope,

two electrodes positioned within said lamp at the respective ends thereof, a trough-shaped metallic reflector strip positioned within said lamp, partly surrounding the discharge and extending substantially the entire length of the discharge path, said strip being electrically separated from each electrode by a respective gap and having a normal width greater than the internal diameter of said tube, whereby said strip is retained in position, said strip reducing light emission from a portion of said lamp.

4. A fluorescent lamp of the positive column discharge type including an elongated glass tube having therein a filling of at least one inert gas and of mercury vapor, two main discharge electrodes within and at the opposite ends of said tube, a metal strip extending substantially the length of the discharge path and electrically separated from each electrode by a gap, said strip being made of resilient metal having a total width greater than the internal diameter of said tube and being deformed from a single plane, whereby said strip is held positioned within said tube, so that one side of said strip partly surrounds the discharge path, said side having thereupon a coating of discrete fluorescent particles.

MILES PENNYBACKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,930,149 Pirani Oct. 10, 1933 1,951,138 Ewest Mar. 13, 1934 2,030,715 Pirani Feb. 11, 1936 2,103,227 Druyvesteyn Dec. 21, 1937 2,112,854 Lucian Apr. 5, 1938 2,135,732 Randall Nov. 8, 1938 2,178,238 Massa Oct. 31, 1939 2,225,712 Price Dec. 24, 1940 2,314,134 Eknayan Mar. 16, 1943 2,364,889 Blair Dec. 12, 1944 2,440,832 Pennybacker May 4, 1948 2,451,043 Pennybacker Oct. 12, 1948 

